1. Field of the Invention
The present invention relates to a call system for making a handsfree call using a microphone and a loudspeaker connected to an information terminal, and for making a handset call using a handset connected to the information terminal.
2. Description of the Related Art
Recently, an Internet Protocol (hereinafter, “IP”) telephone and an Internet telephone for connecting telephone sets to each other through the Internet instead of Public Switched Telephone Network (hereinafter, “PSTN”) have appeared. The IP telephone and the Internet telephone are telephones each using a protocol such as an H.323 or a Session Initiation Protocol (hereinafter, “SIP”). With the IP telephone or the Internet telephone, a microphone (see FIG. 1A) and a loudspeaker (see FIG. 1B) are connected to an information terminal such as a personal computer, and the information terminal, the microphone, and the loudspeaker thus connected can be used as a telephone set for handsfree call as a whole. A handset (see FIG. 1C) is connected to the information terminal such as the personal computer by an interface such as a Universal Serial Bus (hereinafter, “USB”), and the information terminal and the handset thus connected can be used as a telephone set for handset call as a whole.
Prior Art Documents related to the present invention are as follows:
Japanese Patent Application Laid-Open No. 2002-94396
Japanese Patent Application Laid-Open No. 2002-345042
Japanese Patent Application Laid-Open No. 2002-368852
Japanese Patent Application Laid-Open No. 09-224081
Japanese Patent Application Laid-Open No. 2002-506325
Japanese Patent Application Laid-Open No. 2002-536883
According to the conventional Internet telephone, however, the handsfree call and the handset call cannot be freely changed over using the information terminal.